Thermo-electric element.



PATENTED JAN. 31, 1905.

A. L. MARSH. THERMO ELECTRIC ELEMENT.

APPLICATION FILED OOT. 18,1904.

d d C r f 2 [I [IV/1 v i lV/f/ l[, VdV/al m Ii. wv w/ UNiTiEn Squ res Patented January 31, 1905.

PATE T @rricis.

ALBERT L. MARSH, OF LAKE BLUFF, ILLINOIS, AS'SIGNOR TO WILLIAM A. SPINKS & COMPANY, OF CHICAGO, ILLINOIS, A FIRM.

THERMO-ELECTRIC ELEMENT.

SPECIFICATION forming part of Letters Patent No. 781,288, dated January 31, 1905. Application filed October I8, 1904. Serial No. 228,942.

5 invented a new and useful Improvement in Thermo-Electric Elements, of which the following is a specification.

v My objectis to provide an improved thermoelectric element which may be employed with u 1 another element to produce a thermo-electric couple having a particularly high meltingpoint.

I have discovered that the metal chromium, which has a very high melting-point, may,

I particularly when alloyed with nickel, be employed as athermo-electric element electronegative to a nickelcopper element. Such a negative element renders it possible to construct thermo-electric couples of comparao tively great efficiency which may be subjected at their junctions to intense heat without danger of injury. By the term negative element in this connection is meant the element of a pair to which the electric current flows 5 from the other or positive element through the junction of the pair when subjected to heat at the said junction.

This invention is the result of experiments carried on with a view to discovering a readily- 3 0 available metal having a melting-point exceeding, more especially, that of pure copper and which, either alone or when alloyed with other metal or metals, would be either electropositive or electronegative to another highly-refractory metal or alloy with which it could be joined in a thermo-eleetric couple and possess the characteristics above set forth as my object and possess comparatively great strength and durability. I have found that chromium 4 Inay when, alloyed with nickel be formed into a thermo-electric element strongly electronegative to an element formed of an alloy of nickel and copper. Both thevsaid negative and positive elements have melting-points much higher than that of pure copper and may be subjected without danger to intense heat, thereby establishing a difference of electric potential at least equal to any other practical couple of which I am aware without the drawbacks incident to said other couples.

In constructing a thermo-electric battery, for example, I prefer to provide the positive element of each couple of an alloy of nickel (about thirty-five per cent.)and copper, (about sixty-five per cent.) This element has a fusing-pointabove1,050 centigrade. the approximate fusing-point of pure copper. I form the negative element of an alloy of chromium (about ten per cent.) and nickel, (about ninety per cent.) Bars of the alloys named may be readily welded together at their ends to form thermo-electric couples.

The main advantages of a thermo-electric couple constructed of the elements described lie, first, in the great strength and durability of the couple; second, in the fact that as it may be'subjected to heat of great intensity care in the matter of heat regulation is unnections 0 the elements.

In'the accompanying draWing'I show for purposes of illustration a thermopile of one desirable form in cross-section with thermoelectric couples connected in series to form an eflicient thermo-electric generator.

A is a combustion-chamber surrounded by a wall B of highly-refractory material, such as fire-clay, asbestos, or the like.

U 0 indicate thermo-electric couples, each comprising a positive element in the form of a strip aof the nickel-copper alloy mentioned and a negative element in the form of a strip Z) of the chromium-nickel alloy mentioned. The elements of each couple are preferably electrically welded together to form a joint 0, and they pass through the wall B to extend at their joints in the combustion-chamber A. The thermo-electric couples are connected in a common manner by means of strips d, which may be of copper, and the thermopile may have the usual terminals, one of which would erto constructed and of which I am aware,

and they may be subjected to a heat at their inner ends and a cooling action at their outer ends which maintains them at approximately the greatest efiiciency for an indefinite time without affecting their durability to any material extent. The outer end portions of the couples may be air-cooled, or they may be subjected to Water-cooling or other artificial refrigeration.

I have obtained the best results by employing a chromium-nickel alloy in substantially the proportions named for the negative element and a nickel-copper alloy in substantially the proportions named for the positive element. My invention, however, is not in its broad sense to be limited by this statement, as the main point of my invention lies in the discovery of the use of chromium as an element in a thermo-electric couple.

\Vhat I claim as new, and desire to secure by Letters Patent, 1s--- 1. A thermo-electric couple, one element of 4. A thermo-electric couple, one element of which consists of an alloy of chromium and nickel in substantially the proportions set forth.

5. A thermo-electric couple, one element of which consists of an alloy of chromium and nickel and the other element of which is formed in whole or in part of nickel.

6. A thermo-elect-ric couple, one elementot' which consists of an alloy of chromium and nickel and the other element of an alloy of nickel and copper.

ALBER'I. L. M A RS] 1. In presence of- W. N. WINBERG, E. 1:. RICH. 

